Doctor Who: 13 Cool Details Revealed In Steven Moffat's Time Of Angels Commentary
5. Moffat Scripted In Amy Rubbing Her Eye Without Knowing What It Meant
Immediately before everyone heads into the Maze Of The Dead, Amy stays behind for a few seconds and rubs the corner of her eye. This eventually develops into the "Angel in the eye" subplot, but according to Moffat, he actually had no idea what this moment meant when he originally scripted it.
On the commentary, he notes that he simply wanted to end the scene on a cliffhanger. So, he thought that Amy could just rub her eye, and he'd figure the rest out later.
A related point to add here: in followup episode Flesh And Stone, Amy is forced to close her eyes and walk through the forest, unable to see a thing. During the commentary, Moffat says that he always knew he wanted her to do this, but he didn't always know how he would get the plot there.
But clearly, he worked this out by linking up the "eye rub" cliffhanger with the "blind in the forest" idea, so everything turned out well in the end.